Dogs and Wolves Evolved Differently; Study Offers New Insights on Domestication
Analysis of the modern dog and wolf genomes reveals that both the species evolved from a common ancestor, before humans shifted to agricultural societies.
The finding reported in the journal PLOS Genetics reveals that dogs and wolves evolved from a common ancestor between 9,000 and 34,000 years ago. The study further states that dogs are more closely related to each other than wolves, regardless of their geographical origin.
The study also states that any genetic overlap found between modern dogs and wolves is a result of interbreeding after the domestication of the dogs and not because of common ancestry.
This latest study based on the genomes of modern dogs and wolves offers new perspective on dog domestication. Researchers suggest that earlier dogs were a part of the hunter gatherer societies and later adapted to the settled agricultural society
"Dog domestication is more complex than we originally thought," said John Novembre, associate professor in the Department of Human Genetics at the University of Chicago. "In this analysis we didn't see clear evidence in favor of a multi-regional model, or a single origin from one of the living wolves that we sampled. It makes the field of dog domestication very intriguing going forward."
This conclusion was based on analysis of genome sequencing taken from three gray wolves , one each from China, Croatia and Israel. They selected the wolves from these regions as it is believed that dogs basically originated from here. Apart from this the researchers isolated genomes of two dog breeds i.e. a basenji (breed that originates in central Africa) and a dingo from Australia. To serve as an 'outgroup' the researchers also sequenced the genome of a golden jackal.
The analysis of basenji, dingo and boxer genome from Europe revealed that the dog breeds were closely associated to each other. Similarly, the wolves were also more closely related to each other than to dogs. Novembre says that there is a possibility that they all descended from an older, wolf-like ancestor common to both species that went extinct.
According to Adam Freedman, a postdoctoral fellow at the University of California, Los Angeles (UCLA) and the lead author on the study, the aim was to observe the gene flow between dogs and wolves after domestication. The flow of genes across canine species looks to be more pervasive than was previously assumed.
"If you don't explicitly consider such exchanges, these admixture events get confounded with shared ancestry," he said. "We also found evidence for genetic exchange between wolves and jackals. The picture emerging from our analyses is that these exchanges may play an important role in shaping the diversification of canid species."
The analysis also revealed that dogs experienced a 16-fold drop in the population size as they diverged from wolves. A difference in amylase (AMY2B) was noticed in dogs and wolves. This gene helps to digest starch. The researchers argue that the gene was critical in helping theses get settled in domesticated settings.
"We find standing variation in AMY2B copy number in wolves and show that some breeds, such as dingo and husky, lack the AMY2B expansion," said the authors to the LA Times. "This suggests that, at the beginning of the domestication process, dogs may have been characterized by a more carnivorous diet than their modern day counterparts, a diet held in common with early hunter-gatherers."